In this specification, the term “rail tie” refers to cross-ties that are used to attach running rails along a railroad line. Rail ties are typically of a standard length for a given railroad. The term “switch ties” refers to ties used in the vicinity of a switch. Switch ties vary in length along the length of a switch. The more general term “railway ties” encompasses both rail ties and switch ties.
In a railway line, including in the vicinity of a switch, each tie typically has a pair of rail or switch plates (as the case may be) secured to its top surface, one plate being attached to each end of the tie by means of fasteners such as spikes or bolts. Other fasteners extend into the ties and plates and overlap the base of the rails to secure the rails to the ties.
The construction of railway lines often involves securing the plates to the ties in the field (see, for example, U.S. Pat. No. 2,730,962, to Wright et al.). Field installation of plates tends to be slow and requires several individual parts be shipped to the construction site, including ties, plates and spikes. In addition, machinery is required to drill holes into the ties to accommodate screws, or to hammer spikes into the heavy ties. There may also be some difficulty in accurately positioning the plates on the ties.
It is known to pre-plate rail ties in order to simplify and expedite the railway line construction process. Given the required gauge for the line, plates can be attached at a predetermined distance from one end of each tie. The line is then laid out by laying the pre-plated ties and spiking the rails in place.
Examples of pre-plating systems for rail ties are provided in a series of patents issued to Girouard Sr. et al. (U.S. Pat. Nos. 5,343,606; 5,528,807; 5,813,103; 6,119,327; and 6,131,272). Girouard Sr. et al. disclose a pre-plating system wherein a mass of rail ties are aligned and individually loaded onto a conveyor. An individual tie is positioned and secured using an upper and lower template. The system automatically dispenses and positions the rail plates for each tie, using plate cutouts in the upper template. Spikes are automatically fed and positioned using a manipulating arm, then driven through the plates into the tie using a piston shaft press. The plated tie is then discharged via a conveyor system and stacked with other plated ties. U.S. Pat. No. 6,131,272 further discloses a drilling station for making pilot holes and a screw station, if it is desired to attach the plates with lag screws, rather than spikes.
The disadvantages of Girouard et al.'s systems lie in their relative complexity and lack of adaptability. Because the plates are pre-loaded in the plate dispensing mechanism, it is impossible to use different types of plates, as might be required for different rail lines or switches, without stopping the assembly line and re-loading the plate dispenser. Further, aligning the ties properly using upper and lower templates with cutouts through which the plates are set does not allow processing of varying tie lengths, such as switch ties, or ties used in various gauges of rail. Finally, the system apparently does not allow for adjustment according to the particular shape or curvature of any given tie.
U.S. Pat. No. 3,701,320, issued to Fearon et al., discloses another pre-plating system for rail ties. Like the Girouard Sr. et al. systems, Fearon et al.'s pre-plating system is complex and is not readily adaptable to changes in the plates or tie length or shape. In addition, it lacks a drilling station, and therefore requires that the ties be pre-drilled.
Other rail tie pre-plating methods and apparatus are disclosed in U.S. Pat. No. 4,178,671 to Luttig and U.S. Pat. No. 6,292,997 to Ollendick et al. These are simple pre-plating systems, which again lack the ability to optimize the tie plating process and are not adaptable to use with switch ties of varying lengths.
It is therefore an object of the present invention to provide an assembly line whereby railway ties may be accurately pre-plated.
It is a further object of the present invention to provide a pre-plating assembly which is easily adaptable to a variety of tie lengths, such as switch ties, and on which plates may be placed to accommodate any desired gauge.
It is further an object of the invention to provide a pre-plating assembly which can identify a particular tie and drill the tie according to stored data about that tie.
It is yet a further object of the invention to provide an assembly which is capable of scanning a tie and adjusting the pre-stored data to optimize the drilling process.
It is further an object of the invention to provide an assembly line which includes computer-aided inspection of the installed tie plates.
These and other objects of the invention will be appreciated by reference to the summary of the invention and to the detailed description of the preferred embodiment that follow. It will be appreciated that all of the foregoing objectives may not be satisfied simultaneously by the preferred embodiment or by each of the claims.